1. Field of the Invention
The invention relates to modular fixturing systems as used in numerically controlled machining for holding workpieces and in particular to the base or sub-base assembly on which other elements are mounted.
2. Description of the Prior Art
Numerical Control (NC) or Computer Numerical Control (CNC) machines are expensive capital equipment. Their advantages include precision, repeatability and flexibility but the wide range of operations which they are called on to carry out often requires considerable re-tooling and extensive setting up, including the construction of appropriate fixturing to hold the workpiece firmly in position at the required orientation.
In an effort to minimize NC machine down time during set up and to reduce costs, there has been a move away from dedicated hard fixturing to modular systems. Modular fixturing can be quickly set up and torn down as needed, can be easily adjusted for workpiece variations such as inconsistent casting and may be re-used many times over, all significant features in cost reduction.
A number of modular fixturing systems are commercially available. All feature a range of components which are readily interconnected to construct workpiece fixtures as needed. However, in all cases the starting point for constructing the fixturing is essentially the same; a base plate, cube (also known as a column or tombstone) or angle plate. This attaches to the bed of the NC machine and forms the base for the fixturing. The requirements for this base are rigidity and flat surfaces, free from projections.
Heretofore it has been necessary for manufactures of modular fixturing systems to provide and for users to stock these basic elements in a wide range of sizes so as not to limit the size or type of fixturing that may be constructed. Users of NC machines would therefore find considerable advantage in a system for constructing modular fixturing bases in a wide range of sizes and of various shapes from a single type of element provided in a limited range of sizes.